A data scrambling method has conventionally been employed to facilitate detection of timing at a signal change point on a receiver side by averaging changes in amplitude, polarity, and phase of a transmitted signal, even when input data have a periodicity or a constant pattern. In order to realize such a data scrambling method, a data scrambling apparatus has been employed.
Hereinafter, a conventional data scrambling apparatus will be described with reference to figures.
FIGS. 16(a) and 16(b) show a conventional data scrambling apparatus and a conventional data descrambling apparatus, respectively. For simplification, a data scrambling apparatus and a data descrambling apparatus, both employing a generating polynomial, G(X)=1+X.sup.-6 +X.sup.-7, are taken as examples. In FIG. 16, reference numeral 161 designates a data input terminal, numeral 162 designates a scrambled data output terminal, numeral 163 designates registers, numeral 164 designates a mod 2 adder, numeral 165 designates an initialization table, numeral 166 designates a scrambled data input terminal, and numeral 167 designates a data output terminal.
A description is given of the operation of the data scrambling apparatus shown in FIG. 16(a). First of all, initialization values are sent to the respective registers 163 from the initialization table 165 to set initial values. Next, serial data Di are input to the data input terminal 161. The input data are shifted, by one bit for each step, to the subsequent register 163. This shifting of data is successively carried out, and scrambled output data Ds are serially output from the data output terminal 162.
A description is now given of the operation of the data descrambling apparatus shown in FIG. 16(b). First of all, initialization values are set in the respective register 163, and serial data Ds are input to the data input terminal 166. The input data are shifted by one bit for each step, and descrambled output data Do are serially output from the output terminal 167.
Next, a data scrambling apparatus and a data descrambling apparatus which are used in a recording and reproducing apparatus using an optical disk as a medium will be described. In such a recording and reproducing apparatus, generally, scrambling is performed to avoid coincidence of patterns of data recorded in adjacent tracks.
FIGS. 17(a) and 17 (b) show a conventional data scrambling apparatus and a conventional data descrambling apparatus, respectively, employed in an optical disk recording and reproducing device. For simplification, a scrambling apparatus and a descrambling apparatus employing a generating polynomial, G(X)=X.sup.7 +X.sup.6 +1, are taken as examples.
In these figures, reference numeral 171 designates a data input terminal, numeral 172 designates a scrambled data output terminal, numeral 173 designate registers, numeral 174 designates a mod 2 adder, numeral 175 designates an initialization table, numeral 176 designates a scrambled data input terminal, and numeral 177 designates a data output terminal.
A description is given of the operation of the data scrambling apparatus shown in FIG. 17(a). First of all, initialization values are sent to the respective registers 173 from the initialization table 175 to set initial values. Next, serial data Di are input to the data input terminal 171. The initialized data in the respective registers 173 are synchronized with the input data Di and shifted, by one bit for each step, to the subsequent register 173. The shifting of the initialized data and the data input are successively carried out, and data obtained by an exclusive- or operation between the input data and the data output from the register in the rightmost stage are output from the data output terminal 172 as scrambled data Ds.
The operation of the data descrambling apparatus shown in FIG. 17(b) is similar to the operation of the scrambling apparatus shown in FIG. 17(a). That is, scrambled data Ds are input to the scrambled data input terminal 176, and descrambled data Do are output from the data output terminal 177.
As described above, in the conventional scrambling or descrambling apparatus, data are scrambled or descrambled in binary format. In recent years, however, since data are processed with a byte as a unit, it is necessary to convert binary data to byte data, or vice versa.